As the development of the MEMS (Micro-electromechanical system) technology, the piezo-resistive acceleration sensor is extensively applied to many fields, due to a high sensitivity, a fast response, and a low electromagnetic interference. In general, an output of the sensor is a relative low voltage signal, because the signal is low, the signal of the sensor is easily submerged by noise and cannot be recovered. Even the signal is amplified first, but the amplifier generates noise itself and such noise is amplified, such that the SNR (signal to noise ratio) of the amplified signal is also not improved. For the low frequency noise in the signal outputted by the sensor, it is generally removed by adopting a passive RC low-pass filter to filter.
A schematic view of a control circuit of the acceleration sensor is shown as FIG. 1, the control circuit includes an acceleration sensor 101, an anti-aliasing filter 102, and an amplifier 103. The control circuit of the acceleration sensor is also known as an acceleration sensor analog front end which acquires an acceleration signal by the acceleration sensor 101, and the signal outputted by the acceleration sensor 101 is filtered and amplified by the anti-aliasing filter 102, and the acceleration signal is amplified by the amplifier 103 and configured for subsequent operations. The acceleration sensor 101 can be a piezo-resistive acceleration sensor. The model of the piezo-resistive acceleration sensor is represented as one resistor bridge, as shown in FIG. 1. A continuous passive RC filter circuit is generally adopted to accomplish the anti-aliasing filter 102. Generally, the amplifier 103 is a proportional amplifier circuit, the gain of the proportional amplifier circuit is determined by a ratio of the output feedback resistance to the input feedback resistance. In FIG. 1, Vsig represents the signal input end of the acceleration sensor 101, K represents the magnification time of the amplifier 103.
For a continuous passive RC filter circuit, in order to realize a relative low bandwidth, it requires a relative large resistance and capacitance, thus usually leading to a large area of the circuit (chip). At the same time, the sensor is in a working state all the time which causes great power consumption. Because the signal amplitude is relative low, it demands a high requirement for the noise and linearity of the drive circuit, it is difficult to design. The continuous active filter circuit requires using an amplifier, it consumes a large amount of current, and because the non-linearity of the amplifier itself, it causes a signal distortion, therefore, it demands a high requirement for designing the amplifier, increasing a designing difficulty. When the signal through the filter circuit pass through the amplifier circuit, both the traditional resistance proportional amplifier circuit and the switched capacitance proportional amplifier circuit will amplify the noise signal at the time of amplifying the signal, especially for the low frequency noise (1/f noise) of the amplifier itself, therefore, the SNR of the amplified signal decreases, causing the subsequent signal recovering to be more difficult. Further, the passive RC filter circuit does not have a driving capability itself, thus further causing a non-sufficient sampling of the post-stage amplifier circuit.
Therefore, the common used sensor control circuit has problems such as non-sufficient sampling, circuit having a large area, great power consumption and weak noise suppression capability.